Multi-mode display device

ABSTRACT

The present invention relates generally to various arrangements of optical and electronic components to form a high-resolution helmet mounted display (HMD) or other compact display device. In particular, the current invention is designed in such a way as to allow it to operate utilizing several different kinds of image generation device and to incorporate many different features including the option of “eye tracking”.

REFERENCE TO RELATED APPLICATION

[0001] This application claims priority of U.S. provisional patent No.60/213,888 titled “Multi-Mode Display Device” filed Jun. 26, 2000 byAngus Duncan Richards.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] The present invention relates generally to various arrangementsof optical and electronic components to form a high-resolution helmetmounted display (HMD) or other compact display device. In particular,the current invention is designed in such a way as to allow it tooperate utilizing several different kinds of image generation device andto incorporate many different features including the option of “eyetracking”.

[0003] Recently there have been several major breakthroughs in displaygeneration technology. These breakthroughs have occurred in the fieldsof AMLCD, Ferro-Electric Display technology and a new technology knownas LCD on silicon. Display devices will soon be the emerging with XGAand SXGA performance. At this time, it is uncertain which technologywill prevail in the HMD market. This HMD design works equally well withboth transmissive and reflective technologies. When used with atransmissive AMLCD type display device, the HMD design allows thegeneration of a full stereoscopic (separate image to each eye) imagefrom a single display device. This is achieved by “time-multiplexing”the use of the display device between the two eyes. When used with areflective display technology such as FED or LCD on silicon device, aseparate display chip is required for each eye. In addition to theversatility of this display configuration to utilize either of thesedisplay technologies, it is also possible to utilize both of thesedisplay technologies simultaneously. In such a situation, the imagesproduced would consist of an “optical overlay” of the images generatedby the FED and AMLCD devices. Under certain circumstances thisconfiguration can yield great benefits. For example, it would bepossible to provide a large panoramic field of view in relatively lowresolution (perhaps in monochrome) and use the reflective displays toprovide a smaller high-quality field of view as a subset of this largerfield image. It is also possible utilizing this unique HMD design tocombine multiple fields of view utilizing pairs of similar displaytechnology. For example, utilizing a pair of transmissive AMLCD displays(2 displays for each eye) or a pair of FED displays for each eye.

[0004] With the growing interest in “augmented reality” and virtualreality based CAD there is a growing demand for new and more efficientman-machine interface tools. One of the most sophisticated userinterface tools is that of the “eye cursor” or “eye tracking device.”Such “eye cursor” technology calculates the precise direction that eacheye is pointing and mathematically calculates the “target” that is beingviewed. This technology is inherently three-dimensional and representsan ideal interface tool for 3-D virtual worlds and augmented reality.The unique design of this HMD allows the incorporation of eye trackingin addition to the display tasks normally associated with an HMD. Inaddition, the imaging technology that comprises the eye tracking systemcan be used to overcome one of the major problems with lens based HMDdesigns which is the ability to automatically accommodate viewers withdifferent inter-ocular spacing (spacing between the eyes). Mostoff-the-shelf HMD's which are utilizing a lens based design requiremanual inter-ocular adjustment for each viewer. This adjustment is oftendifficult and time-consuming. Both of which, are factors that make suchHMD's inappropriate for public use. By utilizing the imaging hardware ofthe eye tracking system as feedback an automatic or servo controlledinter-ocular adjustment can be readily achieved. Interestingly, suchprecise inter-ocular adjustments are an essential requirement for thecorrect operation of most eye tracking hardware. In this way, bothhardware requirements are met and are mutually symbiotic.

[0005] In certain situations, a “see-through” augmented reality HMDdesign is preferable to a fully enclosed virtual reality configuration.In such a situation it is possible to configure the HMD design describedin this specification to “see-through-mode” by replacing the eyetracking video cameras with corrective optics. This will allow the userto see virtual objects superimposed upon the real world images at thecost of losing the eye tracking and automatic inter-ocular adjustmentfeatures of the design. An alternative configuration which achieves manyof the same objectives is simply to include two miniature video camerasas part of the HMD design. These cameras would provide “real-time” videofeeds which can be digitally combined with the “virtual objects”displayed in the HMD. It would of course be possible to provide the samemonoscopic video signal from a single miniature video camera to botheyes of the HMD however this would preclude the use of eye tracking forall but the virtual objects displayed in the system because eye-trackinginherently requires stereoscopic images to provide the requiredthree-dimensional information.

[0006] In many ways, this electronic equivalent of “see-through mode” isactually superior to the simplistic optical approach as it inherentlyavoids the problems of “transport lag” and “positional inaccuracies”associated with optical superimposing of virtual objects. This ispossible because the same “live video feeds” are being used to determinethe spatial points of reference for the projection of the virtualobjects therefore, any “transport lag” and/or “positional inaccuraciesbetween the “real world” and the “virtual world” are not perceived bythe user because they are common to both the background and the virtualobjects projected upon it. In effect, the user is working entirelywithin a “virtual environment”.

PREFERRED EMBODIMENT

[0007] The preferred embodiment of this design the shown in FIGS. 1,2.The HMD consists of two separate optical assemblies and one optionalcommon optical device. Optical assembly 1 consists of mirror M1,beamsplitter BS1, beamsplitter BS3, eyepiece E1, light source LS3 andoptional components consisting of reflective display device RD1,collimating lens CL1, infrared filter F1, camera ETC1, and infraredlight sources LS1. Optical assembly 2 is basically identical andconsists of mirror M2, beamsplitter BS3, beamsplitter BS4, eyepiece E2,light source LS2 and optional components consisting of reflectivedisplay device RD2, collimating lens CL2, infrared filter F2, cameraETC2, and infrared light sources LS2. The common optical component istransmissive display device TD.

[0008] Mode 1:

[0009] (Reflective Mode—Virtual Reality)

[0010] In this mode two reflective display devices (such as FED orreflective LCD) are used to display a separate image to each eye. Thevideo information delivered to each display device may be purelysynthetic or be a combination of virtual imagery and real-time videofeeds. Although different configurations are possible, beamsplitter'sBS1 and BS2 would generally be of non-polarized type and beamsplitter'sBS3 and BS4 would be of broadband polarizing design. Light sources LS3and LS4 can be of any appropriate type but would most probably be of anLED design. In this configuration, light from light source LS3 wouldpass through beamsplitter BS3. Only light with one plane of polarizationwill be allowed through beamsplitter BS3. The other plane ofpolarization being reflected from the hypotenuse of the beamsplitter. Inthis particular configuration the optional transmissive display elementTD would simply be replaced by a non-reflective baffle. Light beingreflected towards this baffle would simply be absorbed. The reminder ofthe plane polarized light incident upon reflective display device RD1will then selectively undergo rotation of the plane of polarization(phase retardation) depending upon the state of each individual pixel.The light that has undergone this rotation (pixels which are on) willthen be reflected from the hypotenuse of beamsplitter BS3 towardsbeamsplitter BS1. As beamsplitter BS1 is non-polarizing, half of thelight incident upon it will pass through the beamsplitter towards mirrorM1 the other half of the light will reflect off the hypotenuse ofbeamsplitter BS1 towards Infrared filter F1. As light source L3 containsno infrared component, this light will be absorbed by F1. The light thatstrikes concave mirror M1 will form a real image at some distance fromM1 such that the light from this image will once again be partiallyreflected from the hypotenuse of beamsplitter BS1. This reflected lightwill enter E1 and form an image which is viewable by the user of theHMD.

[0011] Ideally, beamsplitter's BS3 and BS1 should be optically bonded toreduce reflections. BS1 and BS2 could be of polarizing design if anadditional phase retarder is placed between beamsplitter BS1 and mirrorM1 (and between beamsplitter BS2 and mirror M2) as shown in FIG. 7. Infact, such a configuration will yield significantly higher opticalperformance. The reason why this is not considered the preferredembodiment is that polarizing beamsplitter's are relatively expensivedevices. It is also possible (at the cost of further reducing systemoptical efficiency) to replace beamsplitter's BS3,BS4 with simple nonpolarizing beamsplitter's and by adding additional polarizers P1-P4 asshown in FIG. 5. which will operate in an optically similar manner.Equally valid is a somewhat simpler configuration utilizing singlepolarizing elements P1, P2 and shown in FIG. 5. These configurations maybe preferable in a production model given that in a furthermodification, the cube beamsplitter's BS1-BS4 could potentially bereplaced by simple partially silvered mirrors which are inexpensive.Reducing the overall optical efficiency may not pose a significantproblem if the light sources LS3 and LS4 are sufficiently powerful. Thereplacement of Cube beamsplitter's with partially silvered mirror stylebeamsplitter's does however have the disadvantage of double reflections.

[0012] The miniature video cameras ETC1,ETC2 work in conjunction witheyepiece lenses E1, E2 to form images of the user's eyes. Infraredfilters F1, F2 are used to block stray light from the display chips fromentering the cameras directly. Light sources LS1, LS2 can be of avariety of different sources and/or different number of light's.However, a configuration of four infrared LED's is probably preferred. Asimple configuration of 4 LED's in a square can be used to achieve botheye tracking and eye positioning (for inter-ocular adjustment). In sucha configuration the LED's will produce four distinct reflections fromthe cornea of the viewer's eyes. This information, in addition to therelative position of the pupil of the eye can be used to determine thedirection that the eye is pointing in 3-D (i.e. a line of sight can bedetermined). The two separate lines of sight (one for each eye) can beused to locate a specific point in 3-D space. Infrared light (or nearinfrared) is used in preference to visible light, firstly because itallows the stray light from the image projection to be easily eliminatedand secondly because the use of visible light would be a constant sourceof irritation to the user.

[0013] In this embodiment of the HMD, eyepiece E1, beamsplitter's BS1,BS3 light source LS3 and reflective display device RD1, collimating lensCL1 and camera assembly consisting of infrared filter F1, light sourceor sources LS1 and camera ETC1 would be physically joined together andwould be free to move laterally as shown in FIGS. 1,2. Mirror M1 is freeto move laterally on the same axes as this assembly and may or may notbe physically connected to the said assembly. The lateral adjustment ofthe aforementioned optical assembly (and its counterpart) allows forautomatic adjustment of different eye spacing (inter-ocular adjustment).This adjustment would ideally be performed by some form of anelectromechanical means such as a servo system. The independentadjustment of the position of mirror M1 will provide focus or diopteradjustment. To reduce costs, the adjustment of mirrors M1, M2 may bedone manually, or alternatively the position of M1,M2 may be fixed withrespect to the separate optical assemblies and focus/diopter adjustmentmay be made directly at the eyepieces E1, E2.

[0014] Mode 2:

[0015] (Transmissive Mode—Virtual Reality)

[0016] In an alternative configuration, the reflective display devicesRD1,RD2 can be replaced by a single transmissive display device (such asan AMLCD). In this configuration stereoscopic images (a separate imageto each eye) can be achieved with a single display element by “timemultiplexing” the two images (i.e. by alternating quickly between eachlight source). This “time multiplexing” is achieved by utilizing twoseparate light sources LS4, LS3 for the illumination of the left andright eye images respectively. It is of course also possible to providethe same image to the left and right eyes simultaneously, simply byswitching light sources LS3, LS4 on at the same time. In many ways thetransmissive configuration is more efficient because only a singledisplay element is required for the generation of two separate images.However, at the present time, reflective display technology issignificantly more advanced than similar transmissive displaytechnology. One of the major differences in the hardware configurationwhen a transmissive element is utilized is that there can no longer be aphysical connection between beamsplitter's BS1, BS3 and BS2, BS4. Inthis configuration beamsplitter's BS3, BS4, light sources LS3, LS4 andtransmissive display device TD form a single optical assembly. Thisleaves optical assembly-1 consisting of beamsplitter BS1, eyepiece E1and optional components infrared filter F1, light sources LS1 andminiature camera ETC1. Optical assembly-2 consists of beamsplitter BS2,eyepiece E2 and optional components infrared filter F2, light sourcesLS2 and miniature camera ETC2. The operation of this modified opticalassembly will be similar to that previously described, with theexception that it is now an absolute requirement that mirrors M1,M2 areadjustable independently from optical assemblies 1,2 in order tomaintain the correct focal position.

[0017] Additional Enhancements:

[0018] With the reflective design, the inclusion of collimating opticsCL1, CL2 (as shown in FIGS. 1-7) can greatly improve the overall opticalefficiency of the system without seriously degrading the image quality.

[0019] Mode 3:

[0020] Reflective focusing optics M1, M2 can be replaced by refractivefocusing optics consisting of lenses FL1, FL2 as shown in FIG. 6.Although theoretically, the mirror elements could be now be eliminatedfrom the design by simply orienting beamsplitter's BS1, BS2 to reflectthe light directly into eyepieces E1, E2 respectively, in practice, thiswould require the focusing optics FL1, FL2 to have an excessively shortfocal length. A more practical solution to this configuration is toreplace concave mirrors M1, M2 with plain mirrors, leaving thebeamsplitter's BS1, BS2 as in the previous configuration. This variationin the design greatly increases the required focal length of optics FL1,FL2 which ease's the design requirements.

[0021] Color Generation:

[0022] The generation of color in this HMD design can be achieved witheither spatial color (red/green/blue picture elements) or by temporalcolor (display of rapid succession of red green and blue image fieldsusually by changing the colour of the light incident on the displaydevice) and is dependent upon the display devices utilized.

[0023] Alternative Configurations:

[0024] The alternative configurations of this HMD as shown in FIGS. 1-7simply highlight alternative configurations for a specific component ofthe overall system. It is of course possible to combine any of theconfigurations shown in FIGS. 1-7 to form an overall system with thedesired characteristics.

[0025] The rotational orientation of the sub assembly consisting oflight source LS3, beamsplitter BS3 and optional components RD1, CL1 andits counterpart consisting of light source LS4, beamsplitter BS4 andoptional components RD2, CL2 is not a factor defining the intellectualproperty and the illustrations showing a particular configuration shouldnot be considered a reduction in the generality of this specification.

1. A compact display device that is capable of utilizing eitherreflective or transmissive display technologies for the generation ofimages for a helmet mounted display device (HMD) or other compactdisplay device.
 2. A compact display device that is capable of utilizinga combination of reflective and transmissive display technologies forthe generation of images for a helmet mounted display device (HMD) orother compact display device.
 3. A display device as described in claims1,2 which generate two separate (stereoscopic) images.
 4. A displaydevice as described in claims 1,2 which generates a single monoscopicimage.
 5. An optical assembly as shown in FIGS. 1,2 which consists ofmirror M1, non-polarized beamsplitter BS1, polarized beamsplitter BS3,eyepiece E1, light source LS3, reflective display device RD1,collimating lens CL1 and optional components consisting of infraredfilter F1, camera ETC1, and infrared light sources LS1.
 6. An opticalassembly (assembly-1) as described in claim 5 and shown in FIGS. 1,2, inwhich light from light source LS3 passes through polarizing beamsplitterBS3 and in doing so becomes plane polarized. This plane polarized lightis then incident upon collimating lens CL1. This light passes throughcollimating lens CL1, becoming partially collimated as it does so. Thispartially collimated light is reflected from the surface of reflectivedisplay device RD1 and in doing so alters the plane of polarization ofthe reflected light according to the state of each individual pixel onthe display device. As this reflected light passes once again throughcollimating lens CL1 it becomes substantially collimated. The reflectedlight which has undergone a rotation in the plane of polarization thenreflects from the hypotenuse of polarizing beamsplitter BS3 and isdirected towards beamsplitter BS1. As beamsplitter BS1 isnon-polarizing, a portion of the light incident upon it will passthrough the beamsplitter towards mirror M1 the other portion of thelight will reflect off the hypotenuse of beamsplitter BS1 towardsInfrared filter F1. As light source L3 contains no infrared component,this light will be absorbed by F1. The light that strikes concave mirrorM1 will form a real image at some distance from M1 such that the lightfrom this image will once again be partially reflected from thehypotenuse of beamsplitter BS1. This reflected light will enter E1 andform an image which is viewable by the user of the HMD.
 7. An opticalassembly as described in claim 5 and shown in FIG. 1, in which cameraETC1 generates an image of the user's eye which is interpreted bydigital processing electronics to determine the position and orientationof the user's eye with respect to the eyepiece E1. This information canthen be used to determine both the correct inter-ocular spacing for theeyepieces and the line of sight for the left eye.
 8. An optical assemblyas described in claim 5 and shown in FIG. 3, in which camera ETC1,infrared filter F1 and light sources LS1 are replaced with correctionaloptics assembly CO1. This optics assembly which consists of a lens orgroup of lenses is designed to generate a real image of the “real world”which will then be optically combined “superimposed” with the projectedimage from optical assembly 1 by virtue of beamsplitter BS1.
 9. Anoptical assembly as described in claims 5-6 and shown in FIG. 4 suchthat polarizing beamsplitter BS3 is replaced with a non-polarizingbeamsplitter and additional plane polarizers P1, P3 are placed betweenlight source LS3 and the beamsplitter BS3 and between the beamsplitterBS3 and beamsplitter BS1 respectively, to achieve a similar opticalcharacteristic.
 10. An optical assembly as described in claims 5-6 andshown in FIG. 5 such that polarizing beamsplitter BS3 is replaced with anon-polarizing beamsplitter and an additional plane polarizer P1 isplaced between beamsplitter BS3 and the reflective display device RD1 toachieve a similar optical characteristic.
 11. An optical assembly asdescribed in claims 5-6 and shown in FIG. 6 such that concave mirror M1is replaced by a combination of lens or lens elements FL1 and planemirror M1 to achieve a similar optical characteristic.
 12. An opticalassembly as described in claims 5-6 and shown in FIG. 7 such thatnon-polarizing beamsplitter BS1 is replaced with a polarizingbeamsplitter and an additional phase retarder PR1 is placed betweenbeamsplitter BS1 and mirror M1 to achieve a similar opticalcharacteristic.
 13. An optical assembly as shown in FIGS. 1,2 whichconsists of mirror M2, non-polarized beamsplitter BS2, polarizedbeamsplitter BS4, eyepiece E2, light source LS2, reflective displaydevice RD2, collimating lens CL2 and optional components consisting ofinfrared filter F2, camera ETC2, and infrared light sources LS2.
 14. Anoptical assembly (assembly-2) as described in claim 13 and shown inFIGS. 1,2, in which light from light source LS4 passes throughpolarizing beamsplitter BS4 and in doing so becomes plane polarized.This plane polarized light is then incident upon collimating lens CL2.This light passes through collimating lens CL2, becoming partiallycollimating as it does so. This partially collimated light is reflectedfrom the surface of reflective display device RD2 and in doing so altersthe plane of polarization of the reflected light according to the stateof each individual pixel on the display device. As this reflected lightpasses once again through collimating lens CL2 it becomes substantiallycollimated. The reflected light which has undergone a rotation in theplane of polarization then reflects from the hypotenuse of polarizingbeamsplitter BS4 and is directed towards beamsplitter BS2. Asbeamsplitter BS2 is non-polarizing, a portion of the light incident uponit will pass through the beamsplitter towards mirror M2 the otherportion of the light will reflect off the hypotenuse of beamsplitter BS2towards Infrared filter F2. As light source L4 contains no infraredcomponent, this light will be absorbed by F2. The light that strikesconcave mirror M2 will form a real image at some distance from M2 suchthat the light from this image will once again be partially reflectedfrom the hypotenuse of beamsplitter BS2. This reflected light will enterE2 and form an image which is viewable by the user of the HMD.
 15. Anoptical assembly as described in claim 13 and shown in FIG. 1, in whichcamera ETC2 generates an image of the user's eye which is interpreted bydigital processing electronics to determine the position and orientationof the user's eye with respect to the eyepiece E2. This information canthen be used to determine both the correct inter-ocular spacing for theeyepieces and the line of sight for the right eye.
 16. An opticalassembly as described in claim 13 and shown in FIG. 3, in which cameraETC2, infrared filter F2 and light sources LS2 are replaced withcorrectional optics assembly CO2. This optics assembly which consists ofa lens or group of lenses is designed to generate a real image of the“real world” which will then be optically combined “superimposed” withthe projected image from optical assembly-2 by virtue of beamsplitterBS2.
 17. An optical assembly as described in claims 13,14 and shown inFIG. 4 such that polarizing beamsplitter BS4 is replaced with anon-polarizing beamsplitter and additional plane polarizers P2, P4 areplaced between light source LS4 and the beamsplitter BS2 and between thebeamsplitter BS4 and beamsplitter BS2 respectively, to achieve a similaroptical characteristic.
 18. An optical assembly as described in claims13,14 and shown in FIG. 5 such that polarizing beamsplitter BS4 isreplaced with a non-polarizing beamsplitter and an additional planepolarizer P2 is placed between beamsplitter BS4 and the reflectivedisplay device RD1 to achieve a similar optical characteristic.
 19. Anoptical assembly as described in claims 13,14 and shown in FIG. 6 suchthat concave mirror M2 is replaced by a combination of lens or lenselements FL2 and plane mirror M2 to achieve a similar opticalcharacteristic.
 20. An optical assembly as described in claims 13,14 andshown in FIG. 7 such that non-polarizing beamsplitter BS2 is replacedwith a polarizing beamsplitter and an additional phase retarder PR2 isplaced between beamsplitter BS2 and mirror M2 to achieve a similaroptical characteristic.
 21. A display device as described in claims 1-3which consists of two separate optical assemblies as described in claims5-20 which are used to deliver a separate image to each eye of the user.22. A display device as described in claims 1-2,4 which consists of asingle optical assembly as described in claims 5-20 which is used todeliver an image to one eye of the user.
 23. A display device asdescribed in claims 1-3,21 that uses the eye position and directioninformation from both the left and right eyes to determine the 3-Dspatial coordinates of the user's gaze.
 24. A display device asdescribed in claims 1-4,21-22 that uses the eye position and directioninformation to determine the “line-of-sight” of the user's gaze.
 25. Adisplay device as described in claims 1-3,21,23,24 that uses the eyeposition information to automatically adjust the lateral position ofoptical assemblies 1,2 (as described in claims 5-20) such that the saidoptical assemblies will be in the optimal position for the display ofimages to the user.
 26. A display device as described in claims1-2,4,22,24 that uses the eye position information to automaticallyadjust the lateral position of a single optical assembly as described inclaims 5-20 such that the said optical assembly will be in the optimalposition for the display of images to the user.
 27. A display device asdescribed in claims 1-3,21,23-25 and shown in FIGS. 1-7 that allows forthe independent adjustment of the lateral position of mirrors M1, M2 inaddition to the lateral adjustment of optical assemblies 1,2 (asdescribed in claims 5-20) such that the said optical assemblies will bein the optimal position for the display of images to the user.
 28. Adisplay device as described in claims 1-2,4,22,24,26 and shown in FIGS.1-7 that allows for the independent adjustment of the lateral positionof mirrors M1, M2 in addition to the lateral adjustment of opticalassemblies 1,2 (as described in claims 5-20) such that the said opticalassemblies will be in the optimal position for the display of images tothe user.
 29. A display device as described in claims 1-3,21,23-25,27and shown in FIGS. 1-7 that incorporates some form of electromechanicalmeans for the adjustment of optical assemblies 1,2 (as described inclaims 5-20) and/or the independent adjustment of mirrors M1, M2.
 30. Adisplay device as described in claims 1-2,4,22,24,26,28 and shown inFIGS. 1-7 that incorporates some form of electromechanical means for theadjustment of a single optical assembly (as described in claims 5-20)and/or the independent adjustment of mirrors M1 or M2.
 31. A displaydevice as described in claims 1-3,21,23-25,27,29 and shown in FIGS. 1-7which consists of two separate optical assemblies as described in claims5-20 which utilize a single transmissive type display device (such as anAMLCD) positioned between beamsplitter's BS3 and BS4 to deliver aseparate image to each eye of the user and which may or may not includethe reflective display devices RD1, RD2.
 32. A display device asdescribed in claims 1-2,4,22,24,26,28,30 and shown in FIGS. 1-7 whichconsists of a single optical assembly as described in claims 5-20 whichutilizes a single transmissive type display device (such as an AMLCD)positioned between beamsplitter's BS3 and BS4 to deliver a separateimage to each eye of the user and which may or may not include thereflective display devices RD1 or RD2 and which may have the lightsource LS3 or LS4 projecting light directly through the transmissivedisplay device in a “back lit” mode of operation as an alternative toutilizing the beamsplitter BS3 or BS4 to reflect the light onto thetransmissive display device.
 33. A display device as described in claims1-3,21,23-25,27,29 and shown in FIGS. 1-7 which consists of two separateoptical assemblies as described in claims 5-20 which utilize a singletransmissive type display device (such as an AMLCD) positioned betweenbeamsplitter's BS3 and BS4 to deliver the same image to each eye of theuser and which may or may not include the reflective display devicesRD1, RD2.
 34. A display device as described in claims1-6,8-14,16-22,27-33 which does not incorporate the optional componentsETC1, F1, LS1, ETC2, F2, LS2.
 35. A display device as described inclaims 1-7,9-15,17-33 which utilizes one or more light sources LS1, LS2as shown in FIG. 1, such that the said light sources will produce astrong reflection or reflections from the cornea of the user's eye inaddition to providing other visual information such as the relativeposition of the user's pupil and/or iris for the purpose of providingthe visual information for determining the position and orientation ofthe user's eye.
 36. An eye tracking module which utilizes the opticalconfiguration as described in claims, 5-7,13-15,35 and shown in FIG. 1which can determine both the position and orientation of an individualeye of the user and from this information can calculate both themis-alignment between the eyepiece optics E1,E2 and the viewer's eye andthe “line-of-sight” for that particular eye
 37. An eye tracking systemwhich utilizes two separate “eye-tracking” modules as described in claim36 which can calculate both the inter-ocular spacing of the particularuser wearing the display system and can determine the 3-D spatialcoordinates of the user's gaze.